that's how it is currently connected. that means that prior to the thermostat opening, the pump will circulate water only on a loop from

- water pump 16mm small inlet - cylinder block - cylinder head temp sensor housing - modine - water pump 16mm small inlet (no water through the rad).

when the theormostat opens, the above loop still exists but we should also have a second water flow:

- water pump main inlet - block - head - thermostat - rad - water pump main inlet

but even though the thermostat has opened to direct hot water to the rad, the rad is 'short circuited' because the water returning from the modine is still re-entering the pump small inlet so there is no incentive for it to flow through the rad. this seems to be a particular issue at idle when there isn't much water flow. do we not need the water out of the modine returning to the cylinder-block-side of the thermostat and then forced to go though the thermostat and rad along with all other water?